Thoughts about loudspeakers

Last edited: Dec. 7, 2019

Explanations of the 'boxy sound', extraordinary speaker designs, full-range drivers, two-way vs. three-way speakers.

The most important component of an audio system is the loudspeaker and the headphone. Modern audio players and amplifiers are so perfect that it makes no sense to talk about audible differences anymore. On the other hand the difference between loudspeakers and headphones is still huge. Most loudspeakers have a nonlinear frequency response (may come from driver resonances, uncompensated baffle diffraction, excessive cabinet edge diffraction, etc.) or other problems (poor off-axis responses). In addition to that the speaker's frequency response will vary according to room size, speaker placement, listening distance... Reflection from the wall behind the speaker and from the floor (or from the table for desktop speakers) is a common problem in room acoustics.

Explanations of the 'boxy sound' - what makes a loudspeaker's sound 'boxy':

Most extraordinary speaker designs have no any sonic advantage over the traditional two-way / three-way speaker design:

Single full-range drivers (aka one-way speakers) are a compromise compared to multi-way speakers. The problem with full-range speakers is that no driver can reproduce the full audio range. Reproduction of bass frequencies requires large cone diameter with large cone excursion. Reproduction of the treble range needs small cone, and the cone excursion is not an important factor. Small full-range speakers (in the 2-3 inch diameter range) have good high frequency reproduction, but limited bass, and on the contrary large full-range speakers have more bass but they lose in the treble. For small desktop speakers, 3 inch full-range drivers are really good choice, because they represent a good balance between size and frequency response.

Two way vs. three way speakers. None of the two designs have any magical qualities compared to the other. Three way design make sense only if the woofer is larger than 6 inches. In this case three way configuration simplifies tweeter selection and crossover design.

The difference between microphone measurements and human hearing has been known for a long time and has been available in the form of measurements since the 1970s (HRTF measurements). This difference is important when interpreting room acoustic issues. For example, due to the directivity of the human ear, the effect of early reflections from a certain angle cannot be corrected with an EQ based on microphone measurements above 500 Hz.

Csaba Horvath

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